Straticharge injector spark plug

ABSTRACT

A spark plug includes an insulating member having a precombustion chamber communicating with one end of the insulating member and including an elongated, substantially cylindrical orifice in the chamber. An electrode rod extends centrally through the member and the precombustion chamber and bears closest to the precombustion chamber adjacent the orifice such that sparking occurs between the end of the rod and the chamber portion opening outward into the orifice.

[111 3,892,991 July 1, 1975 United States Patent [191 Joslyn STRATICHARGE INJECTOR SPARK PLUG Primary ExaminerR. V. Rolinec Assistant Examiner-Darwin R. Hostetter 76 l t D C. l 4732 M ll D 1 men or gg g g l cove T Attorney, Agent, or FirmDuckworth, Hobby & Allen July 1, 1974 Appl. No.: 484,713

[22] Filed:

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FIG. 2

FIG. 4

FIG. 3

STRATICHARGE INJECTOR SPARK PLUG BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ignition devices for internal combustion engines, and in particular relates to such ignition devices which employ precombustion means.

2. Description of the Prior Art Ignition devices for internal combustion engines, commonly referred to as spark plugs, are generally devices which receive an electrical signal to form a spark across a gap between two electrodes and thereby ignite the compressed fuel-air mixture in the piston chamber.

Some types of spark plugs employ a precombustion chamber, sometimes referred to as an antichamber, to create a more concentrated flame front from the sparking device to thereby insure more complete burning and obtain more efficient operation.

An example of a precombustion chamber device like that described above is shown in U.S. Pat. No. 1,162,919 to Hawkins. Hawkins discloses such a device in which an oblong hollow electrode rod extends through the precombustion chamber into the orifice out of the chamber, the rod bearingclosest to the chamber in the orifice to effect sparking at that point.

Other types of precombustion sparking plugs employ an arrangement adapted for receiving commercially available spark plugs of a type which is notoriously well known. Examples of such arrangements are shown in U.S. Pat. No. 753,795 to Hart, and U.S. Pat. No. 2,238,852 to Regar. Other arrangements are likewise disclosed in the following U.S. Pat. Nos. 1,797,817 to Bidwell; 2,702,537 to Wright et al; and 1,127,330 to Westbrook.

In U.S. Pat. No. 1,377,407, Depew discloses a precombustion sparking plug in which the spark-forming electrode comprises a slender rod extending through the combustion chamber and bearing nearest the chamber short of the mouth of the orifice out of the chamber. In the patent to Depew, the chamber walls adjacent the orifice are relatively thin, such that the orifice renders a relatively wide spread flame front out of the precombustion chamber.

SUMMARY OF THE INVENTION The present invention contemplates a spark plug comprising an insulating member and a precombustion chamber communicating with one end of the member, the precombustion chamber including an elongated substantially cylindrical orifice having a sufficient dimension to provide a relatively narrow flame injection out of the chamber. An electrode rod is provided extending centrally through the member in the precombustion chamber, the rod bearing closest to the precombustion chamber, adjacent the orifice.

THE DRAWINGS FIG. 1 is a cross section of one embodiment of a spark plug in accordance with the present invention;

FIG. 2 is a cross section of a tool which may be used in conjunction with the embodiment of FIG. 1;

FIG. 3 is a cross section of a second embodiment of a spark plug in accordance with the present invention;

FIG. 4 is an end view of FIG. 3.

DETAILED DESCRIPTION An embodiment of a spark plug in accordance with the present invention is shown in FIG. 1 and described with reference thereto.

The spark plug, referred to generally as 10, includes an oblong insulated member 12 having a central hollow core 14, the insulating member preferably comprising an aluminum oxide with ceramic material having high heat resistivity and insulation capabilities.

A precombustion chamber 16, defined by a casement 17, communicates with one end of the insulating member 12, the precombustion chamber including an elongated, substantially cylindrical orifice 18 extending from the end opposite the insulation member and substantially axial with the central core 14.

An electrode rod 20 extends through the central core 14 and the combustion chambers 16. The extremity of the rod 20 bears closest to the precombustion chamber 16 adjacent the inner mouth of the orifice 18. A ground electrode 22 encircles the inner mouth of the orifice 18, between the juncture of the orifice and the chamber 16. Preferably, the ground electrode 22 cocmprises a low carbon content metal, such as many of the nickel alloys which are useful in resisting heat and pitting erosion. The extremity of the electrode rod 20 thus bears closest to the ground electrode 22. A conventional terminal connector 24 is coupled to the rod 20 via restrictive air gap 36 at the upper end of the of the insulator member 12.

Again noting the end of the insulating member 12 inside the chamber 16, that end includes a portion 26 extending into the chamber and surrounding a portion of the electrode rod 20.

The spark plug 10 preferably includes sillment seals 28 between the electrode rod and the hollow core 14, and between the insulating member and an outer protective shield 30. The casement 17 further includes cooling fins 34 for providing cooling means in a well known manner. A sleeve 15 bears between the casement l7 and the insulating member 12.

Noting the top of the electrode rod 20, the rod may be separated from the terminal 24 by the air gap 36, described above, in order to intensify the spark; alternatively, a resistor element may be built in along the electrode rod 20, to reduce spurious radio frequency ignition noise. (Note FIG. 3).

As shown in FIG. 1, the spark plug 10 includes a bottom threaded portion 38 for fitting the device in a standard automobile engine, or any internal combustion engine, of the type which includes a piston chamber 40 and at least the orifice 18, the precombustion chamber 16 and the manner in which the electrode rod 20 extends through the chamber 16 and forms a spark gap therewith is designed to give a narrow flame injection toward the top of the piston 42. This is accomplished by providing the orifice 18 with a substantially cylindrical, elongated dimension sufficient to insure that a relatively narrow flame injection 44 is directed only against the central portion of the top face of the piston 42, such that it will thereafter deflect outward toward the walls of the piston chamber 40 to thereby effect a more efficient and complete burning. Preferably, the inner portion of the orifice 18 has a chamfer 19 which is of a sufficient dimension to compensate for the mass of the rod 20 extending into the orifice. In order to accomplish the desired flame injection capability, the orifice 18 is provided with a lengthwise dimension which is at least inches. As will be understood, the diameter of the orifice determines somewhat the parameters of the lengthwise dimension; however, it is believed that this minimum dimension is necessary to provide a relatively narrow flame injection in automobile engines of the type which are in use today.

The operation of the spark plug in accordance with the present invention will now be described. As the piston 42 rises during the compression stroke, the pressure and heat is increased in the piston chamber 40. The fuel air mixture is forced through the orifice 18 at a high velocity. During this period, there is a momentary pressure differential between the piston chamber 40 and the precombustion chamber 16. A spark is then discharged from the electrode rod across the orifice 18 to the ground electrode 22. Combustion begins at that point. As the fuel air mixture is ignited, a flame injection starts to burn in both directions. As described above, the dimensions of the orifice 18 are such as to restrict the flow of burning fuel into the piston chamber 40. This lengthens the effected power stroke of the piston 42 by prolonging the duration of combustion, and reduces the peak pressure in the piston chamber 40, thus eliminating the sudden, hammer-like blow of conventional combustion.

The design of the orifice 18 gives the least fuel-air flow resistence while the mixture is being forced therethrough. In this regard, it should be noted that the orifice 18 is not a venturi, and thus does not cause the injected flame to spread across the head of the piston 42.

Noting FIG. 2, there is shown a tool useful in combination with the spark plug 10 of FIG. 1 in order to effect cleaning of the critical portions of the electrode rod 20. As shown in FIG. 2, the cleaning device, referred to generally as 50, comprises an elongated shaft having a reduced diameter portion 52 and a larger portion 54. It is essential that the reduced diameter portion having an outer dimension equal to or less than the inner diameter of the orifice 18. The reduced diameter portion 52 includes an axial opening 56 having a diameter which is slightly greater than the electrode rod 20.

In use, an amount of sand or similar grit material 58 is placed in the opening 56, and the tool is inserted through the orifice 18. Rotation of the tool 50 then provides a cleaning action at the tip of the electrode rod 20. This tool is useful in the event that the outer sheel and the precombustion chamber casement 17 comprise a single piece as manufactured.

A second embodiment of a spark plug in accordance with the present invention is shown in FIGS. 3 and 4, and is referred to generally as 60. The spark plug 60 is essentially identical to the spark plug 10 shown in FIG. 1, except that an orifice 62 is provided having a portion 64 which is disposed at an angle with respect to movement of the piston. The purpose of the angular portion 64 of the orifice 62 is thus to provide a flame injection which is substantially perpendicular to the face of the piston to effect the narrow flame injection operation described above.

In order to effect cleaning of the electrode rod 20, the embodiment 60 of FIG. 3, the easement 70 thereof is provided with a threaded portion 72 which corresponds to threads 74 on the shell 76, to allow separation of the constituent parts.

Shims 80 are provided between the device 60 and the engine, in order to insure that the proper relationship of the orifice 64 to the piston is attained.

An engine employing the precombustion device of 5 the present invention realizes significantly fewer exhaust emissions than internal combustion engines employing other types ofignition devices. The precombustion device retards formation of the emission gases because cylinder pressure and temperature are more constant throughout the standard operating cycle.

I claim:

1. A spark plug comprising;

an insulating member;

a precombustion chamber communicating with one end of the said insulating member, said precombustion chamber including an elongated, substantially cylindrical orifice extending therefrom, said orifice having a sufficient length so as to provide a concentrated, narrow flame injection therefrom during operation of said spark plug,

a ground electrode about the junction between said chamber and said orifice; and

an electrode rod extending centrally through said member and said precombustion chamber, said rod bearing closest to said precombustion chamber adjacent said ground electrode.

2. The spark plug recited in claim 1 wherein said ground electrode comprises a low carbon content metal.

3. The spark plug recited in claim 1 wherein said insulating member includes a portion extending into said chamber surrounding a portion of said electrode therein.

4. The spark plug recited in claim 3 wherein said electrode is coaxial with said orifice.

5. The spark plug recited in claim 3 wherein at least a portion of said orifice extends at an angle with respect to said electrode.

6. The spark plug recited in claim 3 wherein said precombustion chamber is defined by a casing removably fitted to said insulating member.

7. The spark plug recited in claim 6 further comprising cooling fins along said sleeve.

8. A spark plug adapted for use with an internal combustion engine of the type employing a piston driven by a combustion charge ignited by said spark plug, said spark plug comprising:

an insulating member;

a precombustion chamber communicating with one end of said insulating member, said combustion chamber including an elongated substantially cylindrical orifice extending therefrom and communicating with said engine;

a ground electrode about the junction between said chamber and said orifice;

an electrode rod extending centrally through said member in said precombustion chamber, said rod bearing closest to said precombustion chamber adjacent said orifice; and wherein said orifice has a sufficient length so as to provide a concentrated, substantially uniform flame injection therefrom during operation of said engine.

9. The spark plug recited in claim 8, wherein said orifice includes a portion disposed at an angle with respect 5 to said electrode and substantially perpendicular to said piston. 

1. A spark plug comprising; an insulating member; a precombustion chamber communicating with one end of the said insulating member, said precombustion chamber including an elongated, substantially cylindrical orifice extending therefrom, said orifice having a sufficient length so as to provide a concentrated, narrow flame injection therefrom during operation of said spark plug, a ground electrode about the junction between said chamber and said orifice; and an electrode rod extending centrally through said member and said precombustion chamber, said rod bearing closest to said precombustion chamber adjacent said ground electrode.
 2. The spark plug recited in claim 1 wherein said grounD electrode comprises a low carbon content metal.
 3. The spark plug recited in claim 1 wherein said insulating member includes a portion extending into said chamber surrounding a portion of said electrode therein.
 4. The spark plug recited in claim 3 wherein said electrode is coaxial with said orifice.
 5. The spark plug recited in claim 3 wherein at least a portion of said orifice extends at an angle with respect to said electrode.
 6. The spark plug recited in claim 3 wherein said precombustion chamber is defined by a casing removably fitted to said insulating member.
 7. The spark plug recited in claim 6 further comprising cooling fins along said sleeve.
 8. A spark plug adapted for use with an internal combustion engine of the type employing a piston driven by a combustion charge ignited by said spark plug, said spark plug comprising: an insulating member; a precombustion chamber communicating with one end of said insulating member, said combustion chamber including an elongated substantially cylindrical orifice extending therefrom and communicating with said engine; a ground electrode about the junction between said chamber and said orifice; an electrode rod extending centrally through said member in said precombustion chamber, said rod bearing closest to said precombustion chamber adjacent said orifice; and wherein said orifice has a sufficient length so as to provide a concentrated, substantially uniform flame injection therefrom during operation of said engine.
 9. The spark plug recited in claim 8, wherein said orifice includes a portion disposed at an angle with respect to said electrode and substantially perpendicular to said piston. 